MOSCOW, September 8. /TASS/. Russia has been unable so far to solve a number of vital problems in its relations with Japan and the Kremlin regrets about this, Russian Presidential Spokesman Dmitry Peskov said in an interview with "Moscow. Kremlin. Putin" program on Sunday.

"We regret to say that so far we have failed to solve a number of very important problems," Peskov said.

According to Peskov, the Kremlin views positively cooperation between Moscow and Tokyo in general. "Solutions to such vital issues can be only found based on mutual trust," he noted.

Russia and Japan have been in talks to sign a peace treaty since the mid-20th century. The main stumbling block to achieving this is the ownership issue over the Southern Kuril Islands, called the Northern Territories in Japan. After the end of World War II, the Kuril Islands were incorporated into the Soviet Union. However, the ownership of Iturup, Kunashir, Shikotan Islands and the Habomai Islands has been challenged by Japan. The Russian Foreign Ministry has repeatedly said that Russia’s sovereignty over these islands, which is committed to paper in international documents, cannot be called in question.